1. Field of the Invention
The present invention relates to a fitting structure for knobs particularly suitable for fitting to shaft members of rotation drive members of motors and the like.
2. Description of the Prior Art
To describe a fitting structure for knobs according to the prior art with reference to a drawing, FIG. 6 shows an exploded perspective view of a fitting structure for knobs according to the prior art.
A rotation drive member 51 consisting of an electric motor has a substantially cylindrical body 51a and a columnar shaft member 51b, such as a rotation shaft or the like, protruding outward from the tip of the body 51a. This shaft member 51b is rotated as prescribed by supplying electric power to the body 51a from a terminal (not shown) and, when no power is supplied to the body 51a, the shaft member 51b has a prescribed revolving torque in either the clockwise or the counter-clockwise direction.
A fitting member 52 consisting of a synthetic resin member and formed by molding; a base 53; an annular first fitting portion 54 provided on the same circle as the base 53 sharing the center; and a second fitting portion 55 concentric with and having a greater diameter than the first fitting portion 54. The first fitting portion 54 and the second fitting portion 55 are formed in a collar shape, some protruding outward from the center axis of the base 53.
The base 53 has a front wall 53a formed to be a substantially flat face, and a cylindrical side wall 53b extending backward from the circumference of the front wall 53a. The annular first fitting portion 54 and the second fitting portion 55 are arranged protruding outward from the rear end of the cylindrical side wall 53b. 
The front wall 53a of the base 53 has a round through holes 53c positioned at the center of the front wall 53a. 
A cylindrical member 53d consisting of a metallic material and integrated by insert molding is arranged within the through holes 53c. 
Into the cylindrical member 53d is inserted the shaft member 51b of the rotation drive member 51, and the cylindrical member 53d is fitted to the shaft member 51b with a suitable means such as a screw (not shown). This fitting integrates the fitting member 52 with the shaft member 51b to enable the fitting member 52 to rotate together with the shaft member 51b. 
A knob 56 consisting of a synthetic resin material and formed by molding has a disk-shaped front wall 56a, a cylindrical side wall 56b extending backward from the circumference of the front wall 56a, a plurality (e.g. four) of hooks 57 protruding inward in the cylindrical side wall 56b and positioned on the same circle, and a plurality (e.g. four) of keep pieces 58 protruding inward within the cylindrical side wall 56b and positioned on the same circle. The hooks 57 and the keep pieces 58 are also positioned on the same circle.
In a state in which this knob 56 is arranged in front of and to concentrically cover the fitting member 52, each of the hooks 57 of the knob 56 is engaged with the annular first fitting portion 54, and each of the keep pieces 58 is kept in contact with and over the second fitting portion 55 to couple the knob 56 and the fitting member 52.
This coupling results in arrangement of the side wall 53a of the fitting member 52 within the side wall 56b of the knob 56.
Next will be described how the conventional knob fitting structure described above is assembled.
First, the cylindrical member 53d integrated with the fitting member 52 is fitted to the shaft member 51b of the rotation drive member 51.
Then, the front wall 56a of the knob 56 is arranged over and opposite the front wall 53a of the fitting member 52 to cover the front wall 53a so as to position the side wall 53b of the fitting member 52 within the side wall 56b of the knob 56.
When the knob 56 in this state is pressed in the direction of the axis of the shaft member 51b, the hooks 57 ride over the top of the first fitting portion 54 and are engaged with the first fitting portion 54, and the keep pieces 58 are arranged in contact with and over the second fitting portion 55.
The engaging of the hooks 57 with the first fitting portion 54 and the contact of the keep pieces 58 with the second fitting portion 55 cause the knob 56 to be fitted onto the fitting member 52.
However, the knob fitting structure described above involves the problem that, when the knob 56 is to fitted to the fitting member 52 by pressing in, if the knob 56 is pressed in a state of being inclined relative to the fitting member 52, the fitting member 52 is shaken to make the knob 56 difficult to be fitted and to make the hooks of the knob 56 to be engaged at the same time, adding to the difficulty of fitting.
Also the fitting of the knob 56 in a state of being only hooked onto the fitting member 52 invites the problem that the knob 56 slips relative to the fitting member 52.
An object of the present invention is to solve the problems noted above, and provide a fitting structure for knobs that facilitates fitting of the knob to its fitting member.
A fitting structure for knobs according to the invention is provided with a fitting member fitted to a shaft member and a knob arranged concentrically with the fitting member and fitted to a front face of the fitting member, wherein the fitting member has a base having a flat portion, a stopper protruding forward from the base, and a through hole provided in the flat portion, the knob has a plurality of projections positioned on the same circle, and in fitting the knob to the fitting member, when the knob is rotated while being pressed backward in a state in which the projections are kept in contact with the flat portion, the projections slide on and in contact with the flat portion and when the projections hit against the stopper and the rotation of the knob is stopped, the projections and the through hole become opposite each other to enable the knob and the fitting member to be coupled to each other after the projections are fitted into the through hole.
As this configuration enables the knob to be readily and reliably positioned relative to the fitting member, the fitting is simplified, resulting in a knob fitting structure in which, even if the knob is pressed in a state in which it is inclined relative to the fitting member, the projections enable the knob to be kept in a normal state by the flat portion and reliable coupling of the knob and the fitting member with no fear of slipping of the knob can be ensured.
In the fitting structure for knobs according to the invention, the base has a cylinder protruding forward in its central part, and the projections perform rotary actions with the cylinder as a guide.
This configuration, in which rotary actions are performed with the cylinder as a guide, can provide a knob fitting structure enabling the knob and the fitting member to be reliably coupled while the knob is maintained in an even more normal state.
In the fitting structure for knobs according to the invention, the through hole is formed adjacent to the stopper.
This configuration can provide a knob fitting structure ensuring reliable and easy positioning of the knob, simple and inexpensive assembling, and freedom from slips and excess play of the knob.
In the fitting structure for knobs according to the invention, a plurality of the stoppers and the through holes are provided.
This configuration can provide a knob fitting structure ensuring well balanced, stable and reliable fitting of the knob to the fitting member.
In the fitting structure for knobs according to the invention, the base of the fitting member has an annular fitting portion on the same circle, the knob has a plurality of hooks on the same circle, and the hooks of the knob are engaged with the fitting portion of the fitting member to couple the knob and the fitting member to each other.
This configuration can provide a knob fitting structure that facilitates fitting of the knob to the fitting member and ensures reliable fitting.
In the fitting structure for knobs according to the invention, the knob may have a plurality of keep pieces arranged on the same circle, each of the keep pieces may be positioned between the hooks of the knob, and each of the keep pieces is kept in contact with the fitting portion of the fitting member.
This configuration, as the knob is kept in contact with the fitting portion of the fitting member by the keep pieces, can provide a knob fitting structure in which the knob can be stably fitted to the fitting member.
In the fitting structure for knobs according to the invention, a position in which the fitting portion of the fitting member is engaged with the hooks of the knob is farther outward in a radial direction than a position in which the projections of the knob are fitted into the through hole of the fitting member.
This configuration, wherein the knob is engaged with the fitting member in a position having a greater diameter than the projections of the knob, can provide a knob fitting structure in which the knob can be stably engaged.
The fitting structure for knobs according to the invention is further provided with a rotation drive member of which the shaft member is rotatable, wherein the fitting member is fitted to the shaft member.
This configuration can provide a knob fitting structure enabling rotary action of the knob to achieve its normal coupling to the fitting member.
In the fitting structure for knobs according to the invention, the rotation drive member comprises a motor.
This configuration can provide a less costly knob fitting structure as its rotation drive member comprises a motor of a simple structure.
A fitting structure for knobs according to the invention is provided with a fitting member fitted to a shaft member and a knob arranged concentrically with the fitting member and fitted to a front face of the fitting member, wherein the fitting member has a base, a plurality of arcwise guides protruding forward from the base and provided on the same circle, gaps each provided between adjacent guides, and guide faces each provided at a top of one or another of the guides and inclined relative to the base, the knob has a plurality of projections positioned on the same circle, and in fitting the knob to the fitting member, when the knob is pressed backward in a state in which the projections are kept in contact with the guide faces, the projections are guided on the guide faces, the knob or the fitting member is rotated so as to enable the projections to approach the base and, after the projections are positioned in the gaps, the knob and the fitting member are enabled to be coupled to each other.
This configuration can provide a knob fitting structure which is easy to fit because the knob can be readily and reliably positioned relative to the fitting member and, even if the knob is pressed in a state in which it is inclined relative to the fitting member, the projections enable the knob to be kept in a normal state by the guides and reliable coupling of the knob and the fitting member can be ensured.
In the fitting structure for knobs according to the invention, the projections of the knob are held between adjacent ones of the guides of the fitting member.
This configuration can provide a knob fitting structure ensuring easy positioning of the knob relative to the fitting member, simple and inexpensive assembling, and freedom from slips of the knob.
In the fitting structure for knobs according to the invention, the fitting member is provided with through holes bored in the parts of the base positioned between the gaps, and the projections of the knob are fitted into the through holes.
This configuration can provide a knob fitting structure ensuring even more reliable and easy positioning of the knob, simple and inexpensive assembling, and freedom from slips and excess play of the knob.
In the fitting structure for knobs according to the invention, the projections of the knob are arranged to form a cross.
This configuration can provide a knob fitting structure in which the projections are arranged in a well balanced way, and therefore stable and reliable fitting of the knob to the fitting member is ensured.
In the fitting structure for knobs according to the invention, the guide faces, inclined in the same direction relative to the base, are formed at the tops of the plurality of guides of the fitting member.
This configuration, because the guide faces therein are inclined in the same direction, can provide a knob fitting structure that is simply and inexpensively configured.
In the fitting structure for knobs according to the invention, the base of the fitting member has an annular fitting portion on the same circle, the knob has a plurality of hooks on the same circle, and the hooks of the knob are engaged with the fitting portion of the fitting member to couple the knob and the fitting member to each other.
This configuration can provide a knob fitting structure enabling the knob to be easily and reliably fitted to the fitting member.
In the fitting structure for knobs according to the invention, the knob has a plurality of keep pieces arranged on the same circle, each of the keep pieces is positioned between the hooks of the knob, and each of the keep pieces is kept in contact with the fitting portion of the fitting member.
This configuration, as the knob is kept in contact with the fitting portion of the fitting member by the keep pieces, can provide a knob fitting structure in which the knob can be stably fitted to the fitting member.
In the fitting structure for knobs according to the invention, a position in which the fitting portion of the fitting member is engaged with the hooks of the knob is farther outward in a radial direction than a position in which the projections of the knob are arranged in the gaps.
This configuration, wherein the knob is engaged with the fitting member in a position having a greater diameter than the projections of the knob, can provide a knob fitting structure in which the knob can be stably engaged.
In the fitting structure for knobs according to the invention, the base of the fitting member may have a front wall and a cylindrical side wall extending backward from a circumference of the front wall, the front wall is provided with the guides protruding forward, the knob has a front wall and a cylindrical side wall extending backward from the circumference of the front wall, the front wall of the knob is fitted with the projections protruding backward in a state of being positioned in the cylindrical side wall, and the side wall of the fitting member is positioned within the side wall of the knob.
This configuration can provide a knob fitting structure permitting ready positioning of the knob relative to the fitting member and excelling in assembling ease.
The fitting structure for knobs according to the invention is further provided with a rotation drive member of which the shaft member is rotatable, wherein the fitting member is fitted to the shaft member, and the fitting member rotates together with the shaft member when the knob is fitted.
This configuration provides a knob fitting structure allowing the knob to readily fitted to the fitting member fitted to the rotating shaft member and permitting normal coupling of the knob to the fitting member by pressing the knob in.